1. Field of the Invention
The present invention generally relates to a thermal process of a semiconductor process. More particularly, the present invention relates to a rapid thermal annealing (“RTA”) process of a semiconductor process for monitoring the stability of the RTA process to avoid a failure of wafer.
2. Description of the Related Art
In a semiconductor process, a conventional thermal process includes, for example, annealing after ion implant, solidification, development or annealing of an gate oxide layer, forming reaction of a metal-silicon material, thermal flow or thermal reflow of a borophosphosilicate glass (“BPSG”). A method of performing the conventional thermal process described above includes, for example, using a furnace or a rapid thermal annealing (“RTA”) process. Moreover, compared with the thermal process of using a furnace, the RTA process can complete a thermal process in a relatively short time. Therefore a thermal budget of the RTA process is substantially low and is suitable for a semiconductor process that has to control the diffusion and the contour of doping material.
Referring to FIG. 1, a sectional view of an RTA equipment 100 is illustrated in FIG. 1. When using the RTA equipment 100 for a thermal annealing process, a wafer 104 first is loaded in a wafer loading 106, and the wafer loading 106 with the wafer 104 is then loaded into a reaction chamber 102. Thereafter, the reaction chamber 102 is heated by a heat source 108 to complete the RTA process. In general, a complete RTA process includes, but is not limited to, the following steps, in order: a hold temperature step, a first ramp up step, a stable temperature step, a second ramp up step, a RTA step and a cool down step. The monitoring of the temperature of the reaction chamber 102 is provided by a pyrometer 110 for measuring a thermal radiation of the reaction chamber 102 through a window 112, and the measured thermal radiation is transferred into a temperature of the reaction chamber 102. Then the temperature of the reaction chamber 102 is fedback to a control unit (not shown) of the RTA equipment 100 in order to control the RTA process described above.
However, during the RTA process described above, an instability of the pyrometer 110 may happen as a result of the wafer 104 being attached to the window 112 during the RTA process, or due to a failure of the pyrometer 110 itself. Thus the unstable pyrometer 110 may create an instability of a measured temperature of the RTA process, which, in turn, may disturb the RTA process and damage the wafer 104.